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Memory Foam: Squishing and Snoozing

The inventory includes memory-foam mattress options. Learn why some sleepers are devoted to the stuff with Groupon's exploration.

Bodies are bumpy. That simple truth is a big part of the big appeal of memory-foam mattresses—in 2012, Barron's reported, they commanded 20% of mattress market share and were poised to keep rising. On a regular bed, the heavy parts of your body (such as the hips and shoulders) take on a lot of pressure as you sleep, while others (such as the neck or lower back) receive little support. By letting every part of the body sink in until it reaches a state of supportive equilibrium, memory-foam mattresses spread out the burden, potentially requiring less tossing and turning to relieve pressure points.

If a memory-foam mattress makes you feel as though you're sleeping on air, you're not far off. A block of memory foam is made up of polyurethane riddled with miniscule pockets of air, and as the temperature-sensitive material bends in response to pressure and body heat, the air pockets compress. The material is actually denser than regular mattress foam, so this process of compression is more gradual and controlled. (Consider the difference between squeezing a water balloon and squeezing a water balloon filled with molasses.)

For those who sleep beside someone else or just feel comforted by the presence of their favorite bowling ball, there's another factor that can make for deeper sleep. On a traditional mattress, pressing down on one spring indents the surface all around it. Because the air cells inside memory foam are so tiny, objects deform only the part of the mattress immediately underneath them rather than sending shock waves across the bed.

The first people to experience the comfort of memory foam were wide awake. In the 1960s, NASA engineers developed memory foam for use in aircraft seats, to cushion astronauts by absorbing high-energy impacts more readily. One of the engineers, Charles Yost, later started a company that went on to place versions of the foam in products ranging from shoe insoles to the helmet liners of the Dallas Cowboys.